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Advanced Laboratory Phantoms for Soft Tissues in Engineering and Medicine: ALPHA-STEM

Periodic Reporting for period 1 - ALPHA-STEM (Advanced Laboratory Phantoms for Soft Tissues in Engineering and Medicine: ALPHA-STEM)

Reporting period: 2018-10-01 to 2020-09-30

Research has shown that the success rate in many types of surgeries is strictly related to the experience of the surgeon. However, early in their career, trainees are not given the opportunity to operate on a sufficient number of patients nor to perform an exhaustive mix of procedures.
Training and technical tasks are usually practised on cadavers, animals or using virtual simulators. However, all these alternatives present difficulties: limited availability, expensive handling and preservation processes (cadaveric training), costly set-up, etc. A potential solution is to promote the use of artificial synthetic models, also known as phantoms. Phantoms are reproduction of human parts and organs that allow the trainee to practice positioning of the anatomical structures as well as hand coordination. Unfortunately, they lack of reliable tactile feedback (e.g. palpation) and real tissue deformations which critically reduce the fidelity of the surgical training.

The project’s main objective is the investigation and creation of new materials that can be used to design laboratory phantoms for surgical training.
The main plan starts from the design of novel soft materials, the tuning of their mechanical capabilities (crosslinking agents, network configurations and 3D patterned structures) and finally the development of 3D phantoms of human organs and tissues.

The Objectives are:
To develop multicomponent natural and/or synthetic materials
To investigate the capabilities of the 3D structures in enhancing the nonlinear mechanical behaviour of the materials
To tune the designed materials to mimic the properties of human tissues
To apply the acquired know-how in the design of life-sized phantoms for medical applications and beyond
During the outgoing phase of the fellowship the following work has been completed:
1. Set up a computer with all the software and licences I needed for the project: Matlab, Abaqus (including interlaced configuration with Fortran compiler and VisualStudio to run user-defined subroutines), Mathematica, SolidWorks, OnShape, Adobe Suite, Anaconda (Jupiter notebook +Spyder). Set up the access to the Harvard Odyssey cluster, configure the VPN connection (with double authentication software).
2. Completed training for the Odyssey cluster computer, and on other software that the fellow had not used before: OnShape, Abaqus through Python scripting and Jupiter+Spyder.
3. Completed training on experimental equipment: 1) Universal systems laser cutter, 2) Thinky centrifuge, 3) 3D printers (Ultimaker + Formlab), 4) Instron tensile machine, 5) TorrLab linear stages and DAC.
4. Completed general laboratory training for health and safety protocols, and hazardous chemicals handling.
5. Acquired knowledge on the mechanical characteristics of the human tissues from the literature: stiffness, porosity, viscoelasticity, range of deformations they are usually subjected to.
6. Acquired knowledge on single and multicomponent soft materials and their physical and chemical crosslinking capabilities.
7. Carried out the design of various polymeric networks and characterized them through mechanical testing and chemical analysis.
8. Used mathematical approaches to fit hyperelastic and viscoelastic material models to the preliminary collected data. The fitting routines were coded in Matlab and compared with related results available in the literature. Some of the implemented models included Neo-Hookean, Mooney-Rivlin, Polynomial, Gent and Prony Series formulations, in order to capture the materials’ properties.
9. Designed computer models of 3D patterned structures, including origami, kirigami, and cellular materials (including rotating square patterns). Learnt how to use Periodic Boundary Conditions, User-defined subroutines developed in Fortran, material formulations fitted and instructed by experimental testing and analysis.
10. Developed new manufacturing skills, like laser cutting, polymer coating and 3D printing that were employed to manufacture 3D structures and hybrid structure polymer materials (e.g. kirigami inflatables)
11. Tested and characterized 3D origami, kirigami, rotating square and other cellular structures, collected the data, ran postprocessing analysis along with comparison with computer simulations.
12. Disseminated the new approach for hybrid mechanical metamaterials based on 3D structures and soft polymer science at various conferences and seminars.
13. Published scientific papers on the findings.
14. Presented talks and workshops in group meetings, student events, expert audience, and general public audience (e.g. Researcher’s night 2019).
15. Supervised interns (6 in total), assisting in practical laboratory sessions, mentoring PhD students (2 in total).
The progress beyond the state of the art is the creation of new materials that combine 3D structures with soft polymers. An example of these materials are the kirigami inflatables that have been designed with the future aim of simulating lung tissue, when fabricated at the micro-scale. Unfortunately the microscale fabrication and testing of the materials has not taken place due to the shut down of the labs and facilities cause by the pandemic.

Hopefully the project will manage to deliver life-sized phantoms using the knowledge collected in the outgoing phase of the fellowship, by the end of the return phase. Unfortunately persistent delays due to the pandemic have disrupted (and keeps disrupting) the project's timeline and objective, hindering the delivery of the planned outcomes.

The societal impact of the project will be the availability of phantoms that respond realistically to the touch and can reproduce the deformations of real organs (like the respiratory cycle in the lungs). These will help medical trainees to practise their surgical skills on surrogates before entering the operation room. If, due to the extraordinary circumstances, the project does not achieve this main objective, the research conducted into the material science and design will still be an extremely valuable outcome and a solid base to achieve the creation of the phantoms in the near future.
example of brain laboratory phantom previously developed by the fellow